1. Field of the Invention
The present invention relates to direct current motors and more particularly to a magnetic motor.
A direct current motor constructed in accordance with this invention finds particular application in industry where a high torque direct current motor, having an exceptionally high starting torque, is needed. For example, for starting the diesel engine of a relatively large size truck-tractor commonly referred to as a "big cam Diesel". The engines of these truck-tractors are usually left running in cold weather when the truck-tractor rig is parked out-of-doors for the reason that when the motor and motor oil becomes cold the engine cannot be turned over or started with any presently available starter. This results in an unnecessary waste of Diesel fuel as well as wearing the engine. Further, a direct current motor of this type is needed for mounting on the "dead" axle of a truck-tractor to assist the internal combustion engine on long uphill grades.
2. Description of the Prior Art
The most pertinent prior patents are believed to be my U.S. Pat. Nos. 3,651,355 and 3,723,796. These patents generally disclose multiple armature motors having the axes of the respective armatures arranged in parallel normal to the axis of a coil or coils as in U.S. Pat. No. 3,651,355 or parallel with the coil axis as in U.S. Pat. No. 3,723,796 with both patents featuring magnetic pole pieces surrounding diametrically opposite substantial portions of the respective armature periphery. This partial armature wrap-around feature of the magnetic pole pieces results in a back electromotive force (e.m.f.) opposing the magnetic attractive e.m.f. on the armature winding thus reducing the efficiency of the motor and reducing its torque. In the present invention the back e.m.f. is eliminated by reducing the area of magnetic flux acting on the armature to an arc of the armature circumference spanning the number of the armature segments spanned by the respective armature brush contacting the cooperating commutator segments. This results in forming a motor which has a substantially increased torque when compared with a conventional similar size or rated A.C. or D.C. motor having the major portion of its armature periphery spanned by magnetic pole pieces or conventional field coils.
Other direct current high torque motors presently in use are generally characterized by the disadvantage of a relatively high amperage drag. This feature is particularly undesirable where, for example, the motor is utilized as the prime mover of a vehicle and has a constant amperage drag at a constant voltage whether climbing, cruising or coasting downhill. This invention provides a motor having an amperage drag in proportion to the load and in which the amperage drag is automatically reduced when a cruising speed is reached and is further reduced to a minimum under little or no load.